1. Field of the Invention
The present invention relates to a spindle motor preferably for use in a disk drive apparatus, for example.
2. Description of the Related Art
Some known motors used in disk drive apparatuses include a bearing mechanism using fluid dynamic pressure. For example, a spindle motor disclosed in JP 2009-136143A includes a fixed shaft, an annular bearing component, a rotor component, and an annular cover. The bearing component is arranged at an upper end portion of the fixed shaft. The bearing component is defined integrally with the fixed shaft. The rotor component is arranged outside the fixed shaft. The annular cover is arranged above the bearing component. A radially outer end portion of the annular cover is adhered to an upper end portion of the rotor component. An outer circumferential surface of the bearing component is arranged opposite to an inner circumferential surface of the upper end portion of the rotor component. A seal gap is defined between the outer circumferential surface of the bearing component and the inner circumferential surface of the upper end portion of the rotor component. The seal gap is covered with the annular cover.
As described in JP 2009-136143A, in some motors, a cap member arranged to cover a seal gap is arranged in a rotating portion. In such a motor, the annular cover is arranged to define a labyrinth seal together with an end portion of the shaft, and this reduces exchange of air and accompanying evaporation of a bearing fluid. However, since a gap is defined between the rotating portion and a stationary portion, air including a vaporized lubricating oil leaks out of the motor through this gap. Moreover, an attempt to secure a sufficient rigidity of the cap member by increasing the thickness thereof would prevent a reduction in the thickness of the motor. A reduced thickness of the cap member results in a reduced axial dimension of a gap of the labyrinth seal, leading to increased evaporation of the lubricating oil. Accordingly, there is a demand for a structure which secures a sufficient length of the labyrinth seal while achieving a reduction in the thickness of the motor.